Start up.- suction pressure in cooling on 90 degree day wouldn't go above 70 and head around 300. evap. coil of coarse freezing up, thought it might be expansion valve so we replaced it and that only brought suction up a little, not much. Airflow is fine, removed blower doors and no change in pressures also, fan going right direction, when changing expansion valve blew out lines to see if there was restriction in lines and none were found also no kinks..so I'm out of things, only thing I can think of next would be cap. tubes at evap. coil restricted somewhere..410a system, If anyone has some sudgestions on what to check, I would be greatfull..

is this a txv cooling coil ? if so, what is the suction pressure when the sub-cooling is in the 7-10 degree range ? properly sub-cooled liquid to the valve should result in reasonable superheat unless the valve is not feeding. if it doesn't feed, suction pressure will be low and superheat high....a matched set. if it is fixed, charging until superheat is reasonable should show up a problem. the high pressure switch on 410 probably won't open until discharge pressure exceeds 600 psig. by the time dp exceeds 400 psig, there should be a clue. we're assuming too non-condensables were properly removed.

as we know, ice will form on the coil below 101 psig suction pressure. seems to me both pressures are low. we don't know for sure there is enough freon. i agree we need to know the numbers. i also agree there could be an airflow issue or equipment match problem assuming standard service procedures were followed. it wouldn't hurt to measure the td across the filter/drier.